The above-noted U.S. patents, all of which are assigned to the assignee hereof, disclose compact portable vacuum pumps that find particular utility in evacuating a refrigeration system--e.g., an air conditioning or heat pump system--prior to charging the system with refrigerant. A pump module, containing a single-stage or two-stage rotary vane pumping mechanism, is mounted to one end of an electric motor. The pumping mechanism is rotatably coupled to the motor output shaft for drawing air through an inlet port to the pumping mechanism, and then pumping the air to and through an outlet port. The pumping mechanism is immersed in oil enclosed within the pump module, and baffles are arranged between the outlet of the pumping mechanism and the outlet port to prevent pumping of oil to the atmosphere. A gas ballast communicates with the outlet of the pumping mechanism for selectively admitting dry air to the pump module, and thereby preventing condensation and collection of moisture within the pump module. A handle is affixed to the pump module or motor housing for portability of the pump, and may form part of the pump outlet passage.
Although the vacuum pumps disclosed in the noted patents have enjoyed substantial commercial acceptance and success, improvements remain desirable. It is a general object of the present invention to provide a vacuum pump of the described character having enhanced portability and versatility in operation. A more specific object of the present invention is to provide a vacuum pump of the described character having an inlet valve construction forming a part of the pump itself to isolate the vacuum pump during charging of the refrigeration system following evacuation thereof, while at the same time eliminating any need for disconnecting the vacuum pump from the system and/or providing a separate external inlet valve construction. In connection with the foregoing, it is another yet more specific object of the present invention to provide a vacuum pump having an inlet valve of the described character that may be readily and easily manipulated by an operator for selectively connecting or isolating the vacuum pumping mechanism from the system under service. A further object of the present invention is to provide a vacuum pump of the described character having an improved gas ballast valve arrangement that prevents reverse pumping of oil, for example, through the ballast valve.